JPH05112627A - Production of epoxy resin - Google Patents

Abstract

PURPOSE:To obtain the subject resin having excellent fluidity, moldability, and curing characteristics and useful for molding material, etc., at a low cost from an inexpensive raw material by subjecting specific phenols to aminomethylation in the presence of a solvent and then to epoxidation. CONSTITUTION:A mixed phenol consisting of 5-70mol% monohydric phenol such as phenol and 95-30mol% dihydric phenol such as hydroquinone is subjected to aminomethylation with an aldehyde (e.g. formaldehyde) and ammonium salt (e.g. ammonium chloride) in the presence of a solvent such as alcohol and then the resultant aminomethylated product is epoxidized to provide the objective resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an epoxy resin having a low viscosity at room temperature and its use. Since the epoxy resin according to the present invention gives a cured product having excellent heat resistance, water resistance, and mechanical properties, various molding materials, encapsulating materials and substrates for electronic parts, matrix resins for composite materials, and further adhesives and coating materials. It has a wide range of uses such as.

[0002]

2. Description of the Related Art The FW method (filament winding method) is a method in which a thermosetting resin is impregnated into a reinforcing fiber base material such as glass fiber or carbon fiber and wound around a mandrel, and after the resin is hardened, the mandrel is pulled out. This is a method of manufacturing FRP (fiber reinforced plastic) which is a composite material product. According to the FW method, the fibers can be arranged in arbitrary directions to impart characteristics such as strength and rigidity, and therefore, the method is particularly suitable for producing a high-strength FRP.

A typical thermosetting resin used in the FW method is
Examples include phenolic resins and epoxy resins. High strength F
When manufacturing RP, a low-viscosity liquid resin that is well impregnated into a fiber base material is used. None of the phenolic resins can satisfy both the fluidity and the curing characteristics required for the FW method.

On the other hand, epoxy resins have excellent curing characteristics such as a short curing time and are widely used in various fields. Among the epoxy resins, glycidyl ether of bisphenol A is particularly frequently used in the FW method. But,
Since the obtained cured product has a low glass transition temperature, it cannot be used in a field requiring heat resistance.

In the field where heat resistance is required, a polyfunctional epoxy resin containing phenol novolac as a raw material,
That is, an epoxy novolac resin is used. The epoxy novolac resin has a large number of epoxy groups and thus has improved heat resistance, but is a liquid or solid having a viscous property at room temperature. Therefore, in order to use it for the production of FRP, it is necessary to heat it or dilute it with a solvent to obtain a low-viscosity liquid, which has a problem that the pot life is shortened and the solvent is removed.

Epoxy resin compounds in which phenolic hydroxyl groups are epoxidized by reacting plain resol type compounds such as p-cresol dialcohol and o-cresol dialcohol with epichlorohydrin are also known ( Kiichi Hasegawa et al., "Thermosetting Resin Debate" Proceedings, 1988, p. 121). However, the epoxy resin compounds thus obtained are all crystals or viscous liquids at room temperature and are not suitable for the production of FRP. Also, the glass transition temperature of the cured product of this epoxy resin is 160 at maximum.
The temperature is ℃ and the heat resistance is not sufficient.

Aromatic amine compounds, that is, metaxylylenediamine and diaminodiphenylmethane are respectively reacted with epichlorohydrin to epoxidize amino groups, so that an epoxy resin is a liquid having a low viscosity at room temperature.
Suitable for manufacturing RP (Japanese Patent Publication No. 54-65798 and
59-78177 publication). However, these epoxy resins have a problem in storage stability and, moreover, since a special amino compound is used as a raw material, the raw material is currently expensive for mass production.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the epoxy resin and to develop an epoxy resin which is excellent in heat resistance, fluidity and curing characteristics and is relatively inexpensive. To do. The present inventor has previously proposed a method for producing an epoxy resin using aminomethylated phenol as a raw material (JP-A-3-197525). Epoxy resins using aminomethylated phenols are excellent in that they can simultaneously improve heat resistance, fluidity and curing characteristics, and can be manufactured at a relatively low cost.

Further, as a method for producing this aminomethylated phenol, a method in which a phenol, an aldehyde and an ammonium salt are reacted is effective in suppressing side reactions such as polymerization and is useful as a method for producing a low viscosity epoxy resin raw material. Was proposed (Japanese Patent Application No. 3-90775). According to this method, when phenol is selected as a phenol, formaldehyde is selected as an aldehyde, and ammonium chloride is selected as an ammonium salt, an epoxy resin is synthesized through the following aminomethylation reaction and epoxidation reaction. This method is a general-purpose chemical, phenol,
Since formaldehyde and ammonium chloride are used as manufacturing raw materials, the raw material cost is low and the epoxy resin can be manufactured at low cost.

[0010]

[Chemical 1]

However, even in these methods, when the phenol raw material is a monohydric phenol alone, the obtained epoxy resin is not sufficiently hydrophobic, and when it is stored at room temperature for a long time, the resin is deteriorated due to water absorption or other causes. easy. On the other hand, when the phenol raw material is a dihydric phenol alone, the cross-linking reaction proceeds at a very high density in a three-dimensional manner in the epoxidation step, and an extremely strong cross-linked cured product is produced, so that it has excellent heat resistance. In addition to the expensive raw materials, the yield is low and the cost is high.

[0012]

Means for Solving the Problems The present inventor uses a mixed phenol in which a monohydric phenol and a dihydric phenol are mixed as a raw material phenol in a ratio within a specific range, and a part of the dihydric phenol is monohydric. By synthesizing an epoxy resin with a structure substituted with phenol, the aminomethylation reaction rate,
The inventors have found that the storage stability of the resin and the epoxy group content can be improved, and have reached the present invention.

The gist of the present invention is to provide a method for producing an epoxy resin, characterized in that phenols are aminomethylated with an aldehyde and an ammonium salt in the presence of a solvent, and then epoxidized. Is a mixed phenol of 5-70 mol% monohydric phenol and 95-30 mol% dihydric phenol. The present invention also provides a composite molding material using this epoxy resin and a method for producing FRP by the FW method.

[0014]

The operation of the present invention will be described in detail below together with its operation. The method for producing an epoxy resin of the present invention is carried out by reacting a mixed phenol of a monohydric phenol and a dihydric phenol with an aldehyde and an ammonium salt in the presence of a solvent to effect aminomethylation and then epoxidation.

Aminomethylation reaction (phenol raw material) The phenol raw material used in the present invention is 1
It is a mixed phenol of 5-70 mol% of dihydric phenol and 95-30 mol% of dihydric phenol. When the monohydric phenol is less than 5 mol%, the reaction efficiency is lowered, and it becomes difficult to obtain an epoxy resin having a structure in which a part of the dihydric phenol is replaced with the monohydric phenol. On the other hand, when the amount of monohydric phenol is more than 70 mol%, the aminomethylated product of monohydric phenol and the aminomethylated product of dihydric phenol are separately synthesized, so that the product has two layers and a part of divalent phenols. An epoxy resin having a structure in which is substituted with a monovalent phenol cannot be obtained. Further, the amount of the unreacted phenol raw material exceeds 5%, and it becomes necessary to remove the unreacted phenol by distillation, but the introduction of the distillation step is not preferable as described later.

Phenol, cresol, xylenol, ethylphenol, phenylphenol and the like can be used as the monohydric phenol, and hydroquinone, resorcinol, catechol and the like can be used as the dihydric phenol. The preferred monohydric phenol is phenol in terms of price. The preferred dihydric phenol is hydroquinone. When hydroquinone, which is a p-dihydroxy compound, is used as a dihydric phenol, the reaction efficiency of aminomethylation is increased and the amount of unreacted phenol raw material remaining is reduced, so that an epoxy resin excellent in crosslink density and heat resistance is produced. ..

As the (aldehyde) aldehyde, an aliphatic or aromatic aldehyde such as formaldehyde, acetaldehyde, benzaldehyde, hydroxybenzaldehyde, glyoxal, or an aldehyde-generating substance such as trioxane or paraformaldehyde is used alone or in combination of two or more. can do. Hereinafter, aldehyde will be representatively described with formaldehyde. Formalin, which is an aqueous solution thereof, can also be used as formaldehyde.

As a method of adding formaldehyde, a method of adding the whole amount at the start of the reaction is preferable because the heat resistance of the produced resin becomes high. In the method of gradually adding over a certain period of time, the crosslinking density and heat resistance of the resin decrease.

The amount of formaldehyde used is preferably in the range of 0.5 to 3.0 in terms of molar ratio to the total amount of mixed phenol. When this molar ratio is less than 0.5%, a resin having a low viscosity can be obtained, but the heat resistance of the cured product may be insufficient. Also, the reaction efficiency tends to decrease. In addition, the unreacted material may cause crystals to precipitate on the resin, resulting in poor storage stability. On the other hand, when this molar ratio exceeds 3.0, not only the viscosity of the obtained resin increases but also the yield decreases.

(Ammonium Salt) As the ammonium salt, compounds such as ammonium chloride, ammonium sulfate, ammonium acetate and ammonium carbonate can be used. Further, ammonium and an inorganic acid may be added during the reaction so that these ammonium compounds are produced. Hereinafter, ammonium chloride will be described as a representative of ammonium compounds.

The amount of ammonium chloride used is preferably in the range of 1 to 10 in terms of molar ratio to formaldehyde.
When the molar ratio of ammonium chloride / formaldehyde is less than 1, the reaction efficiency is lowered, so that the epoxy group content of the produced epoxy resin is lowered and the heat resistance is lowered. On the other hand,
If this molar ratio exceeds 10, a large amount of ammonium chloride is mixed in the aminomethylated product, resulting in a decrease in yield and quality of the produced resin.

(Reaction Solvent) As the reaction solvent, alcohols, water and the like can be used, but it is preferable to use water because the reaction rate is high and the heat resistance of the produced resin is improved.

The amount of the reaction solvent used is preferably 0.3 to 3.0 in weight ratio with respect to the total amount of the mixed phenol. If this weight ratio is less than 0.3, the reaction system (monohydric phenol + dihydric phenol + aldehyde + ammonium salt) cannot be mixed and the yield of the product decreases. On the other hand, if it exceeds 3.0, the reaction efficiency decreases.

(Reaction Conditions) The reaction conditions are not particularly limited and may be appropriately determined depending on the properties of the desired aminomethylated product, but may be, for example, the conditions exemplified below.

The aminomethylation reaction of formaldehyde and ammonium salt of mixed phenols is carried out at 60 to 130 ° C.
It is preferable to carry out at the temperature of 0.1 to 10 hours. Reaction time
If it is less than 0.1 hours, the reaction does not proceed sufficiently and the reaction rate decreases. Therefore, unreacted substances are deposited as crystals on the produced resin, and the storage stability is reduced. On the other hand, if it exceeds 10 hours, undesired side reactions such as condensation will proceed and the resin viscosity will increase. The reaction pressure is not particularly limited, but is usually atmospheric pressure.

(Post-Synthesis Treatment) It is desirable to add alcohol to the product after completion of aminomethylation and leave it for a certain period of time. This is because the addition of alcohol can prevent undesired side reactions. The type of alcohol to be added is not particularly limited, but methanol which is easy to separate from water by distillation is preferable. The amount of alcohol used is not limited, but is preferably such that the entire amount of the reaction product is dissolved.

When alcohol is added, the alcohol is removed from the reaction product by distillation after standing for a certain time.
The aminomethylated product containing unreacted material is isolated. Since the condensation reaction is likely to proceed, it is preferable to remove the alcohol by vacuum distillation in order to prevent the reaction. When crystals of ammonium salt are precipitated in the reaction product, it is preferable to remove these crystals before distilling off the alcohol. This is because crystals and aminomethylated substances are mixed after the alcohol is distilled off, and the separation becomes impossible. If necessary, excess catalyst is removed from the product by means such as washing with water.

(Unreacted Phenol) According to this method, as compared with the case where aminomethylation is carried out in a monovalent phenol alone system,
The residual amount of unreacted phenol is as small as 1/15 and does not need to be removed. If a distillation step for removing unreacted phenol is introduced, the aminomethylated product is altered by heating, resulting in higher viscosity of the resulting resin and lower heat resistance.
Therefore, if the step of removing unreacted phenol is unnecessary,
Such a problem can be avoided, which is advantageous. Even if a small amount of unreacted phenol remains, there is no problem because it undergoes epoxidation in the next step and contributes to lowering the viscosity of the resin product.

Epoxidation reaction The thus obtained aminomethylated product of the mixed phenolic raw material is used as a starting material, and this is reacted with epihalohydrin in the presence of an alkali metal hydroxide by a conventional method to give a phenolic hydroxyl group in the aminomethylated product. And a part or all of the N-aminomethyl group is epoxidized to obtain a low-viscosity liquid epoxy resin. Epoxidation proceeds via the addition of epihalohydrin and dehydrohalogenation with alkali metal hydroxide.

As epihalohydrin, epichlorohydrin, epibromohydrin, β-methylepichlorohydrin and the like can be used. The amount of epihalohydrin used is 2.0-
30 times, preferably 3.0 to 25 times.

As the alkali metal hydroxide, sodium hydroxide, potassium hydroxide and the like can be used. The amount of the alkali metal hydroxide used is 0.5 to 4.0 times, preferably 0.8 to 3.0 times, and particularly preferably about the same weight by weight ratio with respect to the raw material aminomethylated product. It is preferable to add the alkali metal hydroxide little by little in a concentrated aqueous solution or granular form to the reaction system. If a large amount is added at once, a local addition polymerization reaction is likely to occur.

The epoxidation reaction can be carried out in one step, but can also be carried out in two steps of addition reaction and dehydrohalogenation reaction (ring closure reaction).

In the case of the two-step reaction, the addition reaction of epihalohydrin to hydroxyl group and amino group is carried out in the coexistence of a phase transfer catalyst at a temperature range of 40 to 150 ° C., preferably 50 to 120 ° C. for 1 to 50 hours. preferable.

The dehydrohalogenation reaction from the addition reaction product is preferably carried out at a temperature range of 40 to 150 ° C., preferably 50 to 100 ° C. for 2 to 50 hours. The water by-produced in the reaction is
It is preferable to carry out the reaction while removing it to the outside of the reaction system by azeotroping with epihalohydrin, and it is preferable to carry out the reaction under reduced pressure to lower the azeotropic temperature in order to prevent polymerization.

After completion of the epoxidation reaction, the epoxy resin product is recovered from the reaction mixture. The resin can be recovered, for example, by recovering epihalohydrin from the resin solution by distillation and then separating the solvent-soluble epoxy resin of the present invention from the alkali metal salt and the solvent-insoluble resin component by solvent extraction.

The solvent used for this solvent extraction is benzene,
Aromatic hydrocarbon solvents such as toluene and xylene, and ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone are preferable. The amount of the solvent used is not particularly limited as long as it is an amount sufficient for extracting the low-viscosity liquid epoxy resin.

The target low viscosity liquid epoxy resin can be isolated by separating the solvent from the obtained extract by distillation.

The low-viscosity liquid epoxy resin obtained by the above-mentioned method of the present invention can be cured using an epoxy curing agent which has been conventionally used. Specific examples of the curing agent that can be used include amine curing agents, polyaminoamide curing agents, acid and acid anhydride curing agents, and the like. Among these curing agents, aromatic amine-based curing agents are particularly preferable because the obtained cured product has a high glass transition temperature and gives a cured product having excellent heat resistance. The amount of curing agent used may be similar to conventional epoxy resins based on the epoxy equivalent of the epoxy resin.

The curing of the epoxy resin of the present invention is considered to proceed by ring-opening polymerization of the epoxy group. In the conventional curing of the resole, there was a problem of foaming due to evaporation of water and condensed water added for lowering the viscosity as described above, but since the epoxy resin of the present invention has a low viscosity itself, It is not necessary to add it, and foaming is not observed in the cured product. This is because the resin of the present invention does not contain water, and because aminomethyl groups are formed, the formation of free methylol groups is suppressed, so that the condensation reaction hardly occurs and the amount of condensed water produced is very small. It is speculated that

This epoxy resin can be used alone for coating, adhesion, various molding applications, or as an electronic component encapsulation or substrate material. Further, it can be advantageously used as a matrix resin of a composite material by taking advantage of the characteristic that it is a low-viscosity liquid, and is suitable for producing FRP by blending reinforcing fibers, for example. Especially FW
It is suitable as a matrix resin when producing FRP by the method.

Other epoxy resins may be mixed and used as long as the useful properties of the epoxy resin of the present invention are not impaired.

[0042]

EXAMPLES The present invention will be specifically illustrated below by showing Examples according to the present invention.

[0043]

Example 1 (Aminomethylation of mixed phenol) Volume 1 equipped with a stirrer, nitrogen introduction tube, thermometer, dropping funnel and reflux tube
A 5-liter flask having a capacity of 5 liters was charged with 71 g of phenol, 83 g of hydroquinone, 161 g of ammonium chloride and 153 g of water, the temperature was started to be raised under stirring, and 122 g of a 37% formalin aqueous solution was added dropwise under reflux at 30 ° C. After completion of dropping, the temperature was raised to 80 ° C. and the reaction was carried out for 1 hour. The starting phenol in this reaction system was a mixed phenol of 50 mol% phenol and 50 mol% hydroquinone, and the formaldehyde / mixed phenol molar ratio was 1.0 and the ammonium chloride / formaldehyde molar ratio was 1.0.

600 cc of methanol was added to the obtained reaction solution and the mixture was allowed to stand overnight for solid-liquid separation, and methanol in the liquid phase was distilled off by an evaporator to give an aminomethylated product.
242 g were obtained. The content of unreacted hydroquinone contained in this aminomethylated product was about 8%, the amount of unreacted phenol was 2%, and unreacted formaldehyde was not detected.

(Epoxidation of aminomethylated product) Stirrer, thermometer, nitrogen introducing tube, dropping funnel, and azeotropic mixture of epichlorohydrin and water are condensed and separated to form epichlorohydrin in the lower layer as a reactor. 57 g of the aminomethylated product obtained above, epichlorohydrin
g, and tetramethylammonium chloride 50% aqueous solution 1
Charge 3.6g, start heating while stirring,
After heating for an hour, the addition reaction of epichlorohydrin was performed.

Then, after raising the temperature of the reaction solution to 85 ° C.,
62 g of sodium hydroxide was added to the flask over about 3.5 hours to complete the ring closure reaction by dehydrochlorination. Further, the mixture was kept for about 30 minutes to completely remove water from the reaction system, and then epichlorohydrin was distilled off by an evaporator.

About 1 liter of toluene was added to the remaining reaction product to dissolve the resin component at room temperature, and the mixture was filtered. Toluene was distilled off from the filtrate by an evaporator to obtain about 68 g of a solvent-soluble low-viscosity liquid epoxy resin product of the present invention. The viscosity of this epoxy resin at 25 ° C. was 1400 cp, the number average molecular weight was 24.8, and the epoxy equivalent (measured by the hydrochloric acid-dioxane method) was 108 g / mol.

(Curing of Epoxy Resin) To the epoxy resin obtained above, 25% of an aromatic amine-based curing agent, ancamine, was added.
Mix in the amount of r, put in a mold, 50 ° C for 1 hour, 70 ° C for 1 hour
C. for 3 hours at 190.degree. 15 of the obtained cured product
The bending strength at 0 ° C. was 6 kgf / mm ² .

[0049]

Example 2 The aminomethylation reaction and epoxidation reaction were carried out in the same manner as in Example 1 except that the phenol raw material was a mixed phenol of 10 mol% phenol and 90 mol% hydroquinone. The amount of unreacted hydroquinone contained in the aminomethylated product was 14.8%, and unreacted phenol and unreacted formaldehyde were not detected. The viscosity of the obtained epoxy resin at 25 ° C. was 1000 cp, the number average molecular weight was 324, and the epoxy equivalent was 101 g / mol.

Ancamine as a curing agent was mixed with the epoxy resin in an amount of 37% phr, and the mixture was placed in a mold and cured at 50 ° C. for 1 hour, 70 ° C. for 1 hour, and 190 ° C. for 3 hours. The flexural strength of the obtained cured product at 150 ° C. was 6 kgf / mm ² .

[0051]

Comparative Example 1 (Aminomethylation of Phenol) A solution of 94 g of phenol and 54 g of ammonium chloride dissolved in 265 g of water was charged in the same 5-neck flask as used in the aminomethylation step in Example 1. Then, the temperature rise was started under stirring, and 81 g of 37% formalin aqueous solution was added dropwise under reflux at 50 ° C. After completion of dropping, the temperature was raised to 60 ° C. and the reaction was carried out for 1 hour. The formaldehyde / phenol molar ratio in this reaction system was 1.0, and the ammonium chloride / formaldehyde molar ratio was 2.

100 cc of methanol was added to the obtained reaction solution, and the mixture was allowed to stand overnight for solid-liquid separation, and methanol in the liquid phase was distilled off by an evaporator. Further, 5% aqueous sodium hydroxide solution was added to neutralize the solution to pH 8, oil-water was separated, and the oil was concentrated to obtain 83 g of aminomethylphenol. The content of unreacted phenol contained in this was about 16% by weight, and unreacted formaldehyde was not detected.

(Epoxidation of aminomethylphenol) In a 5-neck flask similar to that used in the epoxidation step in Example 1, 83 g of the aminomethylated product obtained above, 660 g of epichlorohydrin, and tetramethylammonium chloride were added. 30
A solution obtained by dissolving 60 g of water in 60 g of water was charged, the temperature was raised with stirring, and the mixture was heated at 100 ° C. for 2 hours to carry out an addition reaction of epichlorohydrin.

Then, after lowering the temperature of the reaction solution to 70 ° C.,
121 g of sodium hydroxide was added to the flask over about 3.5 hours to complete the ring closure reaction by dehydrochlorination. Further, the above reaction conditions were maintained for about 30 minutes to completely remove water from the reaction system, and then epichlorohydrin was distilled off by an evaporator.

About 2 liters of toluene was added to the remaining reaction product to dissolve the resin component at room temperature, followed by filtration. Toluene was removed from the filtrate by an evaporator to obtain about 165.8 g of a solvent-soluble low-viscosity liquid epoxy resin product of the present invention.
Got The viscosity of this epoxy resin was 900 cp at 20 ° C., the number average molecular weight was 406, and the epoxy equivalent was about 157 g / mol.

(Curing of epoxy resin) The liquid epoxy resin obtained above was mixed with ancamine as a curing agent in an amount of 23% phr, placed in a mold and cured at 70 ° C for 1 hour and 190 ° C for 3 hours. It was As a result, a high-strength cured product was obtained. The flexural strength of the obtained cured product at 150 ° C. was 5 kgf / mm ² .

[0057]

Comparative Example 2 DER 330 (manufactured by Dow Chemical Co., Ltd.), which is a commercially available bisphenol A glycidyl ether type epoxy resin, was mixed with 23% phr of ancamine and cured under the same curing conditions as in Comparative Example 1. The flexural strength of the obtained cured product at 150 ° C. was 4 kgf / mm ² .

[0058]

According to the method of the present invention, an epoxy resin produced by aminomethylating an aldehyde and an ammonium salt with a mixed phenol of a monohydric phenol and a dihydric phenol as a raw material and then epoxidizing the same, Despite being a low-viscosity liquid at room temperature, it can be cured in the same curing time as conventional epoxy resins, and the cured product has good water resistance and mechanical properties. In addition, the cured product of this epoxy resin is superior in strength at high temperature as compared with conventional epoxies, and exhibits heat resistance as high as that of resole. Furthermore, this epoxy resin
It has excellent moldability, can be cured in a shorter time than conventional resoles, does not cause foaming problems, and has a long pot life, resulting in excellent workability.

Due to such characteristics, the low-viscosity liquid epoxy resin produced by the method of the present invention can be used as various molding materials, encapsulants and substrates for electronic parts, matrix resins for composite materials, adhesives and coating materials. Can be used for applications such as FRP production, especially FR by the FW method.
It is suitable for the production of P.

Claims (3)

[Claims] 1. A method for producing an epoxy resin, which comprises subjecting a phenol to aminomethylation with an aldehyde and an ammonium salt in the presence of a solvent, and then epoxidizing the resulting aminomethylated product. A method for producing an epoxy resin, which is a mixed phenol of 5 to 70 mol% of a dihydric phenol and 95 to 30 mol% of a dihydric phenol. 2. A molding material containing the epoxy resin obtained by the method according to claim 1 and a reinforcing fiber. 3. A method for producing a fiber reinforced plastic product by a filament winding method using the epoxy resin obtained by the method according to claim 1.